Two kinds of large neurones were studied in histological preparations and electron micrographs of the parenchyma of the anterior region of the body, the pharynx and the oral and ventral suckers of Fasciola hepatica. These are called the α and β neurones. The latter are larger than the α cells and vary in structure. An interstitial system composed of amorphous material of medium electron density was observed in the parenchyma, the suckers and the pharynx. Invaginations of the plasma membrane containing interstitial material extend into the β neurones and are often continuous with the nuclear envelope. It is suggested that the β cells are neuro-secretory in function and that they may be derived from the α neurones.

Morphology and histology of the males of Acanthobonellia miyajimai (Ikeda) and Acanthobonellia vulgaris Menon and DattaGupta have been described. The males of the two species are large and look alike in all respects. Ciliated epithelium, subepidermal glands and two to four seminal vesicles are characteristics of these worms. The alimentary canal is in the form of a chain of vesicles which appear to be a common feature of Acanthobonellia, Acanthohamingia or Ikedella. Anatomical features have been described and figured.

Monthly quantitative samples of the invertebrate fauna were taken from two stations in the River Endrick over a period of fifteen months; the substrate at one station in the lower reaches was sandy, whilst that at the other in the middle reaches was stony. The fauna at these stations differed qualitatively, but showed certain quantitative similarities, especially with regard to seasonal change. The fauna of stones is richer, and much more varied than that of sand, though both substrates appear to be unstable and may be drastically affected by spates. The average standing crop of the invertebrate fauna during 1960 was found to be 8 g. per square m. in sand and 16 g. per square m. in stones. Compared with the few other results which are available for rivers elsewhere in the world these figures would indicate that the standing crops of these substrates in the River Endrick are of intermediate richness.

The previous history of Allenopithecus is summarized and a new description provided based on freshly dead cadavers of an adult male and female and of a male stillborn infant. Analysis of details of body proportions and external anatomy confirm the apartness of Allenopithecus from Cercopithecus and indicate a transitional status towards the macaques. Striking departures from cercopithecine features occur in the face, ear, extremities, in the presence, in the female, of a catamenial swelling and in the approximation or confluence, in the male, of the ischial callosities.

A squash-preparation technique for the measurement of nucleus lengths in permanent preparations of the spermatozoa of Drosophila melanogaster is described. Prefixation gave longer nuclei, but the degree of pressure used in making the squash did not affect nucleus length. Variation in nucleus length between the spermatozoa of a male was fairly high (coefficient of variation 14 per cent). Smaller, though significant, differences existed between means of males within culture bottles, but there were no significant differences between means of duplicate culture bottles. There was a little evidence of heterogeneity of within-male variances. A logarithmic transformation of data before analysis was indicated. These observations provide a hitherto missing background for planning experiments in quantitative variation designed to throw light on genetic and other factors affecting the dimensions of Drosophila spermatozoa.